Electrostatic particle separators are used to separate different types of small particles by using their electrostatic attraction and repulsion properties. Generally the mixture of particles to be separated is conveyed along a flat surface from a feed hopper to a rotating separation roll. The final treatment of the particles is to feed them as a thin layer onto the rotating roll, which then rotates the particles through an electrostatic field to charge some of the particles so as to enhance the separation process. In machines which accomplish these treatments it is necessary to bring the velocity of the particle movement up to approach as closely as possible the surface velocity of the roll, so that the layer of particles is easily transferred to the roll with a minimum of agitation. Such machines are shown in our patents U.S. Pat. Nos. 4,421,148 and 4,849,099 for use in separating fine particles, where the final particle velocity is reached by dropping the particles down a vertical chute to be accelerated by gravity to the appropriate velocity for discharge onto the drum. It is the purpose of the present invention to accomplish a separation of coarse particles wherein the final particle acceleration does not include vertical falling, since that tends to incorporate a certain amount of unwanted bounce or agitation of the particles.
Prior art wide tray feeders usually have included a plurality of electromagnetic vibratory drive units spaced along its width, as illustrated for example by the FMC wide spreader feeder at page E-12, of Catalog 100, 1983, "FMC Corporation Syntron and Link Belt Material Handling Equipment". Rather than the multiple electromagnetic vibratory drive units used in the FMC wide spreader feeder, the invention herein employs a single rotating motor with eccentric weights to achieve the requisite vibratory feeder to accelerate the particles. Thus, uneven feeding along the width of the tray due to a number of factors, including the multiple drive units becoming out of synchronization, causing eddy currents in the feed bed. In accord with this invention, the tray's vibration throughout the width experiences one amplitude of vibration and moves the feed bed uniformly of the width of the tray. Attendant advantages include a much more compact design occupying less volume within an electrostatic particle separator, for example.
It is an object of this invention to provide a novel apparatus for presenting or delivering coarse particles onto a conveyor. It is another object of this invention to provide a novel apparatus for electrostatic separation of particles in which the particles being fed to a separation roll are accelerated to the proper speed by moving down a vibrated inclined plane. A further object is to provide an accelerating means which breaks up agglomerates of the particles and feeds a single thickness of particles onto an electrostatic separating means. Still other objects will become apparent from the more detailed description which follows.